Kratom leaves contain psychoactive chemicals, including mitragynine, that are mu-opioid agonists with some similarity in effects to opium-poppy opiates and pharmaceutical opioids. The primary health concerns for most users are sedation-related risks, addiction/dependence, constipation, itchiness, and possible liver health problems.

We know of no documented deaths directly attributable to kratom, but some products sold as kratom have resulted in death. One death documented in a 2011 paper described a kratom product that also had O-desmethyltramadol (a synthetic pharmaceutical) added to it.1

According to Pascal Tanguay, from the Thailand offices of PSI, a Washington DC-based global health organization that promotes harm reduction among drug users, "There's never been a single death associated with kratom. People have been chewing this for thousands of years with no cases of overdose, psychosis, murder, violent crime. Never in all of recorded history."2

Liver Toxicity / Hepatotoxicity / Hepatitis.
A small number of kratom experience reports describe hepatitis and/or hepatotoxic symptoms. This effect has also been reported in the medical literature (Kapp et al. 2011). Most of these reports of liver-health issues involve kratom extracts rather than unenhanced dried leaves. It is unknown if these are attributable to kratom alkaloids, extract-production byproducts, or other contaminants. See Sly 2008, Nlogn 2011, Experience Reports with mentions of liver issues.

Habituation / Addiction.
Kratom is considered addictive; reports of physical and psychological dependence, tolerance, and physical withdrawal symptoms are prevalent, though not universal, in experience reports. Taking kratom daily can result in physical dependence. In such instances, symptoms similar to those of opioid withdrawal usually begin 18-24 hours after the last dose and continue for 1-14 days.

Vomiting while Sedated
Mixing kratom with alcohol or other sedating drugs could result in life-threatening situations related to aspiration of vomit and asphyxia if unattended.

People are afraid of opioid analgesics because they can lead to respiratory depression [difficulty breathing]. When you overdose on these drugs, your respiratory rate drops to zero. In animal studies where rats were given mitragynine, those rats had no respiratory depression. This opens the possibility of someday developing a pain medication as effective as morphine but without the risk of accidentally overdosing and dying.
- Boyer E (professor of emergency medicine and director of medical toxicology at the University of Massachusetts Medical School.)3

Medical Uses.
The primary medical uses described by users of kratom are analgesia (pain relief), cessation of opioid withdrawal symptoms, and sedation.

Reduction or Cessation of Opioid Withdrawal Symptoms
Kratom is widely used by opioid addicts to stop or reduce opioid withdrawal symptoms. In some cases, kratom use helps individuals stop taking opioids entirely, but in other cases kratom simply replaces the other opioid addiction with daily kratom use.